1. Field of the Invention
The present invention relates to foaming technology and more particularly, to a microbubble creating method for creating microbubbles in fluid polymer using a forming machine.
2. Description of the Related Art
Foam manufacturing technologies can be classified as mechanical foaming, physical foaming and chemical foaming. In the mechanical foaming, bubbles are created by using an agitator to stir a gas into the fluid polymer. In the physical foaming, heat produces a low boiling liquid which evaporates, thus forming the bubbles. In the chemical foaming, the blowing agent reacts under the influence of heat, releasing gases, which forms the voids in the fluid polymer beads obtained through the suspension polymerization.
Further, U.S. Pat. No. 7,264,757 discloses a different technique in which a gas delivery pipe is embedded in a feed screw, and a plurality of microporous breathable blocks is mounted at the front end of the feed screw. When a high pressure gas is delivered into the gas delivery pipe, the high pressure gas is heated in an indirect manner and then guided through the micro holes of the microporous breathable blocks into the fluid polymer, and thus, the high pressure gas is mixed with the fluid polymer subject to rotation of the feed screw, and then the mixture of the high pressure gas and the fluid polymer is filled into a mold, causing creating of microbubbles in the fluid polymer.
In the aforesaid prior art structures, the microporous breathable blocks are embedded in air vents in the feed screw in flush with the surface of the feed screw, thus, the microporous breathable blocks can only be kept in contact with the surface of the fluid polymer and will not be surrounded by the polymer, thus, the supplied gas cannot be fully mixed with the fluid polymer, resulting in uneven distribution of generated microbubbles in the fluid polymer.